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Triceratops
Triceratops (pronounced /traɪˈsɛrətɒps/) is an extinct genus of herbivorous ceratopsid dinosaur which lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago (mya) in what is now North America. It was one of the last dinosaur genera to appear before the great Cretaceous–Tertiary extinction event.Lehman T.M., 1987 Late Maastrichtian paleoenvironments and dinosaur biogeography in the Western Interior of North America, from the Journal of Paleogeography, Paleoacclimatology and Paleoecology, vol. 60, pp. 290. Bearing a large bony frill and three horns on its large four-legged body, and conjuring similarities with the modern rhinoceros, Triceratops is one of the most recognizable of all dinosaurs. Although it shared the landscape with and was preyed upon by the fearsome Tyrannosaurus,Fowler, D. W., and Sullivan, R. M. (2006). A ceratopsid pelvis with toothmarks from the Upper Cretaceous Kirtland Formation, New Mexico: evidence of late Campanian tyrannosaurid feeding behavior. New Mexico Museum of Natural History and Science Bulletin 35:127–130. it is unclear whether the two battled the way they are commonly depicted in movies, children's dinosaur books and many cartoons. A complete Triceratops skeleton has yet to be found;The Ultimate Dinosaur Book, 1993, by Lambert, D.; pp. 152–167. Published by Dorling Kindersley, New York, ISBN 1-56458-304-X however, the animal is well-known from numerous partial remains collected since the introduction of the genus in 1887. The function of their frills and three distinctive facial horns has long inspired debate. Although traditionally viewed as defensive weapons against predators, the latest theories claim that it is more probable that these features were used in courtship and dominance displays, much like the antlers and horns of modern reindeer, mountain goats, or rhinoceros beetles.The Horned Dinosaurs, 1996, by Dodson, P. Published by the Princeton University Press, Princeton, New Jersey, ISBN 0-691-02882-6 Triceratops is the best-known of the ceratopsids, though the genus's exact placement within the group has been a point of contention amongst paleontologists. Two species, T. horridus and T. prorsus, are considered valid, although many other species have been named. Description Individual Triceratops are estimated to have reached about 7.9 to 9.0 m (26.0–29.5 ft) in length, 2.9 to 3.0 m (9.5–9.8 ft) in height,DinoDictionary.com :: T Dinosaurs Page 2Triceratops in The Natural History Museum's Dino Directory and 6.1–12.0 tonnes (13,000-26,000 lb) in weight.Alexander, R.M. (1985). "Mechanics of posture and gait of some large dinosaurs." Zoological Journal of the Linnean Society, 83, 1–25. The most distinctive feature is their large skull, among the largest of all land animals. It could grow to be over 2 m (7 ft) in length, and could reach almost a third of the length of the entire animal. It bore a single horn on the snout, above the nostrils, and a pair of horns approximately 1 m (3 ft) long, with one above each eye. To the rear of the skull was a relatively short, bony frill. Most other frilled dinosaurs had large fenestrae in their frills, while the frills of Triceratops were noticeably solid. Triceratops species possessed a sturdy build, with strong limbs and short five-hoofed hands and four-hoofed feet. Although certainly quadrupedal, the posture of these dinosaurs has long been the subject of some debate. Originally, it was believed that the front legs of the animal had to be sprawling at angles from the thorax, in order to better bear the weight of the head. This stance can be seen in paintings by Charles Knight and Rudolph Zallinger. However, ichnological evidence in the form of trackways from horned dinosaurs, and recent reconstructions of skeletons (both physical and digital) seem to show that Triceratops maintained an upright stance during normal locomotion, with the elbows slightly bowed out, in an intermediate state between fully upright and fully sprawling (as in the modern rhinoceros).Christiansen, P., and Paul, G.S. (2001). Limb bone scaling, limb proportions, and bone strength in neoceratopsian dinosaurs. Gaia 16:13–29.Chapman, R.E., Snyder, R.A., Jabo, S., and Andersen, A. (2001). On a new posture for the horned dinosaur Triceratops. Journal of Vertebrate Paleontology 21 (Supplement to Number 3), Abstracts of Papers, 61st Annual Meeting:39A–40A. This conclusion does not preclude a sprawling gait for confrontations or feeding. Classification Triceratops is the best known genus of the Ceratopsidae, a family of large North American horned dinosaurs. The exact location of Triceratops among the ceratopsians has been debated over the years. Confusion stemmed mainly from the combination of short, solid frills (similar to that of Centrosaurinae), and the long brow horns (more akin to Ceratopsinae, also known as Chasmosaurinae). In the first overview of horned dinosaurs, R.S. Lull hypothesized two lineages, one of Monoclonius and Centrosaurus leading to Triceratops, the other with Ceratops and Torosaurus, making Triceratops a centrosaurine as the group is understood today.Hatcher, J. B., Marsh, O. C. and Lull, R. S. (1907) The Ceratopsia. Government Printing Office, Washington, D.C. ISBN 0405127138. Later revisions supported this view, formally describing the first, short-frilled group as Centrosaurinae (including Triceratops), and the second, long-frilled group as Chasmosaurinae.Lambe, L.M. (1915). On Eoceratops canadensis, gen. nov., with remarks on other genera of Cretaceous horned dinosaurs. Canada Department of Mines Geological Survey Museum Bulletin 12:1–49.Lull, R. S. (1933) A revision of the Ceratopsia or horned dinosaurs. Memoirs of the Peabody Museum of Natural History 3'(3):1–175. In 1949, C.M. Sternberg was the first to question this and favoured instead that ''Triceratops was more closely related to Arrhinoceratops and Chasmosaurus based on skull and horn features, making Triceratops a ceratopsine (chasmosaurine of his usage) genus.Sternberg, C. M. (1949). The Edmonton fauna and description of a new Triceratops from the Upper Edmonton member; phylogeny of the Ceratopsidae. National Museum of Canada Bulletin '''113:33–46. However, he was largely ignored with John Ostrom,Ostrom, J. H. (1966). Functional morphology and evolution of the ceratopsian dinosaurs. Evolution 20:220–227. and later David Norman, both placing Triceratops within Centrosaurinae.Norman, David; The Illustrated Encyclopaedia of Dinosaurs. Published 1985, by Salamander Books, in London. ISBN 0-517-468905 Subsequent discoveries and analyses upheld Sternberg's view on the position of Triceratops, with Lehman defining both subfamilies in 1990 and diagnosing Triceratops as ceratopsine (chasmosaurine of his usage) on the basis of several morphological features. In fact, it fits well into the ceratopsine subfamily, apart from its one feature of a shortened frill.Lehman, T. M. (1990). The ceratopsian subfamily Chasmosaurinae: sexual dimorphism and systematics. in: Carpenter, K., and Currie, P. J. (eds.). Dinosaur Systematics: Perspectives and Approaches, Cambridge University Press, Cambridge, pp. 211–229. ISBN 0-521-36672-0. Further research by Peter Dodson, including a 1990 cladistic analysisDodson, P., and Currie, P. J. (1990). Neoceratopsia. 593–618. in Weishampel, D. B., Dodson, P., & Osmólska, H. (eds.). The Dinosauria University of California Press:Berkeley, pp. 593–618. ISBN 0-520-06727-4. and a 1993 study using RFTRA (resistant-fit theta-rho analysis),Dodson, P. (1993). Comparative Craniology of the Ceratopsia. In: American Journal of Science 293, pp. 200–234. a morphometric technique which systematically measures similarities in skull shape, reinforces Triceratops' placement in the ceratopsine subfamily. Use in phylogenetics In phylogenetic taxonomy, the genus has been used as a reference point in the definition of Dinosauria; Dinosaurs have been designated as all descendants of the most recent common ancestor of Triceratops and Neornithes (i.e. modern birds).Gauthier, J. A. (1986). Saurischian monophyly and the origin of birds. The Origin of Birds and the Evolution of Flight, K. Padian (ed.), Memoirs of the California Academy of Sciences 8':1–55. Furthermore, the bird-hipped dinosaurs, Ornithischia, have been designated as all dinosaurs with a more recent common ancestor to ''Triceratops than modern birds.Sereno, P. C. (1998). A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen '''210(1):41–83. Origins of eastern Colorado. Based on the age of the Laramie Formation, it may be the oldest Triceratops known.]] For many years the origins of Triceratops have been largely obscure. In 1922, the newly discovered Protoceratops was seen as its ancestor by Henry Fairfield Osborn,Dodson, P. (1996). The Horned Dinosaurs. Princeton University Press:Princeton, New Jersey, p. 244. ISBN 0-691-02882-6. but many decades passed before additional findings came to light. However, recent years have been fruitful for the discovery of several dinosaurs related to ancestors of Triceratops. Zuniceratops, the earliest known ceratopsian with brow horns, was described in the late 1990s, and Yinlong, the first known Jurassic ceratopsian, in 2005. These new finds have been vital in illustrating the origins of horned dinosaurs in general, suggesting an Asian origin in the Jurassic, and the appearance of truly horned ceratopsians by the beginning of the late Cretaceous in North America.Dodson, P., Forster, C. A, and Sampson, S. D. (2004) Ceratopsidae. In: Weishampel, D. B., Dodson, P., and Osmólska, H. (eds.), The Dinosauria (second edition). University of California Press:Berkeley, pp. 494–513. ISBN 0-520-24209-2. As Triceratops is increasingly shown to be a member of the long-frilled Ceratopsinae subfamily, a likely ancestor may have resembled Chasmosaurus, which thrived some 5 million years earlier. History Etymology The term Triceratops, which literally means "three-horned face", is derived from the Greek tri/τρι-'' meaning "three", ''ceras/κέρας meaning "horn", and ''-ops/ωψ'' meaning "face".Liddell & Scott, 1980; Greek-English Lexicon, Abridged Edition. Published by the Oxford University Press, Oxford, UK. ISBN 0-19-910207-4 Discoveries and species The first named specimen now attributed to Triceratops is a pair of brow horns attached to a skull roof, found near Denver, Colorado in the spring of 1887.Carpenter, K. (2006). [https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/Balticornis.pdf "Bison" alticornis and O.C. Marsh's early views on ceratopsians.] In: Carpenter, K. (ed.). Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs Indiana University Press:Bloomington and Indianapolis, pp. 349–364. ISBN 0-253-34817-X. This specimen was sent to Othniel Charles Marsh, who believed that the formation from which it came dated from the Pliocene, and that the bones belonged to a particularly large and unusual bison, which he named Bison alticornis.Marsh, O.C. (1887). Notice of new fossil mammals. American Journal of Science 34:323–331. He realized that there were horned dinosaurs by the next year, which saw his publication of the genus Ceratops from fragmentary remains,Marsh, O.C. (1888). A new family of horned Dinosauria, from the Cretaceous. American Journal of Science 36:477–478. but he still believed B. alticornis to be a Pliocene mammal. It took a third and much more complete skull to change his mind. The specimen, collected in 1888 by John Bell Hatcher from the Lance Formation of Wyoming, was initially described as another species of Ceratops.Marsh, O.C. (1889a). Notice of new American Dinosauria. American Journal of Science 37:331–336. After reflection, however, Marsh changed his mind and gave it the generic name Triceratops, accepting his Bison alticornis as another species of Ceratops''Marsh, O.C. (1889b). Notice of gigantic horned Dinosauria from the Cretaceous. ''American Journal of Science 38:173–175. (it would later be added to Triceratops). The sturdy nature of the animal's skull has ensured that many examples have been preserved as fossils, allowing variations between species and individuals to be studied. Triceratops remains have subsequently been found in the American states of Montana and South Dakota (in addition to Colorado and Wyoming), and in the Canadian provinces of Saskatchewan and Alberta. Number of species Within the first decades after Triceratops was described, various skulls were collected, which varied to a lesser or greater degree from the original Triceratops, named T. horridus by Marsh (from the Latin horridus; "rough, rugose", suggesting the roughened texture of those bones belonging to the type specimen, later identified as an aged individual). This variation is unsurprising, given that Triceratops skulls are large three-dimensional objects, coming from individuals of different ages and both sexes, and which were subjected to different amounts and directions of pressure during fossilization. Discoverers would name these as separate species (listed below), and came up with several phylogenetic schemes for how they were related to each other. In the first attempt to understand the many species, Lull found two groups, although he did not say how he distinguished them: one composed of T. horridus, T. prorsus, and T. brevicornus; the other of T. elatus and T. calicornis. Two species (T. serratus and T. flabellatus) stood apart from these groups. By 1933, and his revision of the landmark 1907 Hatcher-Marsh-Lull monograph of all known ceratopsians, he retained his two groups and two unaffiliated species, with a third lineage of T. obtusus and T. hatcheri that was characterized by a very small nasal horn. T. horridus-''T. prorsus''-''T. brevicornus'' was now thought to be the most conservative lineage, with an increase in skull size and a decrease in nasal horn size, and T.-elatus-''T. calicornis'' was defined by large brow horns and small nasal horn. C. M. Sternberg made one modification, adding T. eurycephalus and suggesting that it linked the second and third lineages closer together than they were to the T. horridus lineage. This pattern was followed until the major studies of the 1980s and 1990s. With time, however, the idea that the differing skulls might be representative of individual variation within one (or two) species gained popularity. In 1986, Ostrom and Wellnhofer published a paper in which they proposed that there was only one species, Triceratops horridus.Ostrom, J. H., and Wellnhofer, P. (1986). The Munich specimen of Triceratops with a revision of the genus. Zitteliana 14:111–158. Part of their rationale was that generally there are only one or two species of any large animal in a region (modern examples being the elephant and the giraffe in modern Africa). To their findings, Lehman added the old Lull-Sternberg lineages combined with maturity and sexual dimorphism, suggesting that the T. horridus-''T. prorsus''-''T. brevicornus'' lineage was composed of females, the T.calicornis-''T.elatus'' lineage was made up of males, and the T. obtusus-''T. hatcheri'' lineage was of pathologic old males. His reasoning was that males had taller, more erect horns and larger skulls, and females had smaller skulls with shorter, forward-facing horns. These findings, however, were contested a few years later by Catherine Forster, who reanalysed Triceratops material more comprehensively and concluded that the remains fell into two species, T. horridus and T. prorsus, although the distinctive skull of T. hatcheri (now Nedoceratops) differed enough to warrant a separate genus.Forster, C.A. (1996). Species resolution in Triceratops: cladistic and morphometric approaches. Journal of Vertebrate Paleontology 16(2):259–270. She found that T. horridus and several other species belonged together, and T. prorsus and T. brevicornus stood alone, and since there were many more specimens in the first group, she suggested that this meant the two groups were two species. It is still possible to interpret this reasoning as describing a single species with sexual dimorphism.Lehman, T. M. (1998). A gigantic skull and skeleton of the horned dinosaur Pentaceratops sternbergi from New Mexico. Journal of Paleontology 72(5):894–906. Valid species *''T. horridus'' (Marsh, 1889) (originally Ceratops) (type species) *''T. prorsus'' (Marsh, 1890) Doubtful species The following species are considered nomina dubia ("dubious names"), and are based on remains that are too poor or incomplete to be distinguished from pre-existing Triceratops species. *''T. albertensis'' (C. M. Sternberg, 1949) *''T. alticornis'' (Marsh, 1887 (originally Bison)) *''T. eurycephalus'' (Schlaikjer, 1935) *''T. galeus'' (Marsh, 1889) *''T. ingens'' (Lull, 1915) *''T. maximus'' (Brown, 1933) *''T. sulcatus'' (Marsh, 1890) Misassignments *''T. brevicornus'' (Hatcher, 1905) (=''T. prorsus'') *''T. calicornus'' (Marsh, 1898) (=''T. horridus'') *''T. elatus'' (Marsh, 1891) (=''T. horridus'') *''T. flabellatus'' (Marsh, 1889) (=''T. horridus'') *''T. hatcheri'' (Lull, 1907) (=''Diceratus hatcheri'') *''T. mortuarius'' (Cope, 1874) (nomen dubium; originally Polyonax; =''Polyonax mortuarius'') *''T. obtusus'' (Marsh, 1898) (=''T. horridus'') *''T. serratus'' (Marsh, 1890) (=''T. horridus'') *''T. sylvestris'' (Cope, 1872) (nomen dubium; originally Agathaumas sylvestris) Gallery References Category:Threehorns Category:Fourfooters Category:Dinosaurs